For all retirement allowances due on or after July 1, 1974, the retirement allowance payments to any member retired prior to said date or his beneficiary designated under an optional benefit or to any other beneficiary in receipt of an allowance prior to said date, exclusive of payments under the Supplemental Allowance Program, shall be recomputed as though the provisions of Section 9-11-60(2), (a) of this chapter had been in effect at the time of his most recent retirement. Any such benefits payable under the Supplemental Allowance Program shall be increased by ten percent effective July 1, 1974. This section shall not, however, be applicable to the part of any retirement allowance derived from a member's accumulated additional contributions.
Benefits payable due to retirement prior to July 1, 1988, shall be increased by fourteen and three-tenths percent effective July 1, 1988.
Benefits payable due to retirement before July 1, 1989, must be increased by seven percent effective July 1, 1989.